The present invention relates to a composite bumper system including a reinforcement beam with molded components that optimize energy absorption of the bumper system.
It is known to roll-form or stamp a high strength beam as an initial step in constructing a vehicle bumper. For example see U.S. Pat. Nos. 5,092,512 and 5,454,504. A problem is that, after roll forming, several additional secondary processes must be performed before the beam can be used as a vehicle bumper. For example, mounting bracketry must be attached to the beam to provide for attachment of the beam to a vehicle. The mounting bracketry is usually attached by a secondary process, such as welding, which requires significant investment in welding equipment and also requires close process control. Additional secondary processes and/or metal end attached parts are often used to shape ends of the bumper to meet design demands, such as to provide an aerodynamically styled bumper that sweeps at the front corners of the vehicle. However, these metal end-attached parts and end-forming processes are often expensive and add considerable cost to a bumper system. Sometimes, flexible plastic end caps are used to trim out ends of the bumper. However, flexible plastic end caps do not provide corner impact strength, but instead are designed to flex out of the way while other structure provides impact resistance. It is desirable to provide a mounting arrangement that simplifies or eliminates much of the secondary processing and that reduces the number and cost of the secondary processes, but that provides structure to ends of the bumper for corner impact strength and for styling. Another problem is that bumper beams must be made very strong to withstand the high impact forces generated in a vehicle crash. A bumper beam that collapses prematurely or inconsistently will not pass government tests. However, it is also undesirable to have a beam that is so stiff that it absorbs very little energy during impact, because the unabsorbed energy is transferred directly to the vehicle and results in damage to other vehicle components. Optimally, the beam should flex in a manner absorbing a maximum amount of energy over a given stroke during the impact, so that crash forces are optimally spread out over the bumper stroke during impact in a manner minimizing damage to the vehicle. Improvements are desired that utilize the flexibility and moldability of plastics, but in a way that does not make the bumper sensitive to premature or inconsistent failure due to a low impact strength and crack sensitivity of structural plastics or their sensitivity to cold (or hot) environments.
Accordingly, a bumper construction solving the aforementioned problems and having the aforementioned advantages is desired.